1. Field of the Invention
The present invention relates to a fuel injection control arrangement for an internal combustion engine, in particular, to a fuel injection control arrangement for an internal combustion engine capable of detecting abnormality of a fuel pressure control means and/or fuel pressure detection means in the arrangement.
2. Conventional Art
When an internal combustion engine is operated under a condition of superlean air/fuel ratio, for example, 30.about.100 with respect to stoichiometric air/fuel ratio of 14.7, an extreme improvement in fuel economy and in exhaust gas clarification performance can be achieved, however, in order for operating the internal combustion engine at such superlean air/fuel ratio a highly pressurized fuel is necessary. In an operation of an internal combustion engine, a predetermined constant fuel pressure is frequently employed. However, in order to achieve a sufficient combustion performance it is preferable to vary the fuel pressure, for example, it is preferable to control the fuel pressure between 5 MPa and 10 MPa depending upon operation modes of an internal combustion engine concerned. For the purpose of this fuel pressure control, an electrically controllable pressure regulator for regulating the fuel pressure and a fuel pressure sensor for detecting the fuel pressure are used. However, in case when one of the electrically controllable fuel pressure regulator and the fuel pressure sensor fails, there poses a problem that the fuel pressure is placed out of control.
JP-A-10-47144 (1998), for example, discloses an abnormality diagnosis device for a fuel supply and injection arrangement which detects abnormality in fuel pressure and performs an abnormality diagnosis in the arrangement, wherein the abnormality diagnosis device for the fuel supply and injection arrangement, which includes a fuel pressurizing pump for pressurizing fuel in order to inject the pressurized fuel from a fuel injection nozzle into an internal combustion engine, a solenoid valve for adjusting amount of fuel to be fed and injected from the fuel injection nozzle into the internal combustion engine and a solenoid control means for outputting driving signals for the solenoid valve so as to control the amount of fuel at a predetermined amount, the abnormality diagnosis device is provided with a fuel pressure detection means for detecting the fuel pressure and an abnormality judging means of the solenoid valve based on variation of fuel pressure after being outputted of a valve open signal to the solenoid valve from the solenoid control means.
When an abnormal increase or decrease in fuel pressure in the fuel supply and injection arrangement or system for an internal combustion engine is detected, a failure which deteriorates an operating performance of the internal combustion engine can generally be discovered, however, a possible cause of the failure can not be judged by the detection of the fuel pressure abnormality. Further, if it is erroneously diagnosed as a failure, a corresponding element is erroneously exchanged.